Maple syrup is made from the sap of maples trees. In cold climate areas, the trees store starch in their roots and trunk before the winter; the starch is then converted to sugar and rises in the sap in the spring. Maple trees can be tapped and the exuded sap collected and concentrated by heating to evaporate the water. The average maple tree will produce about 50 liters of sap per season. To obtain one liter of maple syrup, about 40 liters of sap must be boiled.
Maple syrup consists primarily of sucrose (more than 60% by weight) and water, with small amounts of minerals and other sugars such as fructose and glucose. The mineral content of the maple syrup is mainly potassium and calcium. Scale formation and deposit on the base and side walls of the primary evaporation pan is a recurrent maintenance problem for maple syrup producers. In maple syrup production, the circulating sap tends to remain stationary for some time during the evaporation cycle, thus allowing minerals to precipitate from the sap and adhere to the base and side walls of the pan. Over time, a number of layers of calcium and potassium based scale can aggregate on the base of the evaporation pan, and in particular in the narrow channels formed between adjacent base flues.
Scale build up compromises performance of maple syrup production since operation of the evaporating pan must be stopped regularly for cleaning and removal of the scale. The operator of the evaporator has to change the whole primary evaporator pan or has to drain and wash the same pan every time the scale deposit obstructs the flow. The operator first needs to stop the supply of heat, to let the temperature of the sap lower and to rinse the large evaporator pan. The whole operation can take several hours. Moreover, once a new primary evaporator pan is installed, the thermal resilience of the new sap in the primary evaporator pan needs supplementary energy to increase the temperature in order to meet again the required temperature for boiling. The supplementary consumption of energy means additional cost for the producer and additional polluting emissions for the environment.
Scale build up on the base of the primary evaporator pan may also cause burning of the maple syrup. As soon as the mineral sedimentation starts to caramelize on the base of the evaporator pan, as a result of the heat, the smell and the taste of burnt maple syrup can spread through all the sap that circulates in the evaporator pan. This situation may cause a loss of production or a deterioration of the quality of the product.